Project Abstract This is an application for renewal and reorganization of a longstanding program for predoctoral training at Harvard Medical School designed to integrate across disciplinary boundaries. Over the last funding cycle, combined modernization and expansion of the four-decade old parent program (Cellular and Developmental Biology) have led us to rename our current program, Molecular, Cellular and Developmental Dynamics (MCD2), to signal an increase in intellectual breadth and depth, as well as multiple programmatic innovations, that will improve the quality of the training experience offered to our students. The mission of the MCD2 program (http://cellbio.med.harvard.edu/mcdd/) is to train future leaders at the forefront of discovery that will investigate the fundamental organizing principles and dynamics of molecules, cells, and tissues. Our goal is to build versatile and independent scholars capable of advancing important scientific frontiers with rigorous and novel approaches. To accomplish this, we offer a coordinated curriculum with emphasis on transferrable skills in experimental design, quantitative analysis, and project development. In addition to four compulsory Research Skills courses, our students select a series of Quantitative Analysis and Core Content courses to complement their existing strengths and scientific vocabulary. Our program has consistently led the forefront of educational innovation within the Harvard landscape, producing novel courses and training activities, such as our new Innovation Grant Program to fuel bold yet rigorous student-initiated proposals, and our new ?Big Data? curriculum to equip trainees with the analytical skills required for discoveries that will stand the test of time. MCD2 brings together a community of deeply committed scientists and educators to deliver this innovative program, and to provide our trainees with rigorous and supportive research training mentorship. Our preceptor group spans a multi-disciplinary spectrum of expertise, ranging from molecular cell biology to organismal development and physiology. This creates an environment where students learn to think across boundaries of scale, model system, and approach. To strengthen this environment, we also organize a rich array of paracurricular activities that promote scientific communication and collaboration, and enrich the community. Each year we will select a cohort of 18 MCD2 predoctoral students from a pool of over 200 talented candidates in multiple Harvard Integrated Life Science (HILS: http://www.gsas.harvard.edu/hils/) graduate programs. MCD2 members will be supported by this grant during their second and/or third year of PhD training, after Dissertation Advisor and research focus have been selected. As our trainees progress to degree completion, we also offer an assortment of professional development activities, workshops, and resources to prepare them for success at the next stage of their careers. While the majority of our trainees pursue careers in research and medicine, we also appreciate that many other professions are required to bring biomedical discoveries into clinical and other applications.